双氟磺草胺在不同类型土壤中的吸附与淋溶特性研究

农药在土壤中的吸附和淋溶特性是评价其环境行为的重要指标。采用批量平衡法和土柱淋溶法,研究了双氟磺草胺在小麦种植区3种代表性土壤中的吸附和淋溶特性。结果表明:双氟磺草胺在安徽黏土、山东砂质壤土和河南砂质黏壤土中的吸附规律均可以较好地用Freundlich方程描述,其吸附系数(Kf)在0.39~0.62之间;土壤有机碳归一化吸附系数(Koc)在66.91~81.35之间,表明双氟磺草胺在3种土壤中均属于难吸附型;吸附自由能(ΔG)在-10.90~-10.42kJ/mol之间,均属于物理吸附。双氟磺草胺在3种土壤中的淋出率在71.7%~74.1%之间,说明其在3种土壤中的淋溶性均较强。双氟磺草胺初始添加量和腐殖酸对淋出率具有一定影响。综合试验结果,认为双氟磺草胺在3种土壤中的吸附和淋溶可能受土壤有机质含量、黏粒含量、阳离子交换量和土壤pH值等多个因素的综合影响,其对地下水的污染风险较大,因此应引起高度重视。

Adsorption and leaching behavior of florasulam in different soils

The adsorption and leaching of pesticides in soils are important evaluation index which can be used to describe it’s environmental behavior. In this study, the adsorption and leaching of florasulam in different soils were conducted by batch equilibrium and column leaching experiments. The results showed that the adsorption of florasulam in the tested soils was better fitted by the empirical Freundlich adsorption isotherm, and the adsorption constants (Kf) in Anhui clay, Shandong sandy loam and Henan sandy clay loam were ranged from 0.39 to 0.62. The organic carbon partition coefficients (Koc) were ranged from 66.91 to 81.35, which demonstrated that florasulam was rather difficult to be adsorbed on the tested soils. The values of adsorption free energy (ΔG) in the three soil samples were ranged from–10.90 to –10.42 kJ/mol. And the adsorption belonged to spontaneous and physical process. In the three soils, the leaching rates were ranged from 71.7% to 74.1%, and florasulam showed comparatively high mobility and leaching degree. The initial addition and humic acid had some effect on the leaching rate. The adsorption and migration of florasulam could be influenced by the combined effects of organic matter content, clay content, C.E.C and pH value of soil. Thus attention should be paid to the pollution problem of groundwater caused by florasulam.